Device to increase the resolving power in projections on a translucent screen, particularly fit for photogrammetric appliances



June 1, 1965 G- PARENTI 3,186,299

DEVICE TO INCREASE THE RESOLVING POWER IN PROJECTIONS ON A TRANSLUCENTSCREEN, PARTICULARLY FIT FOR PHOTOGRAMMETRIC APPLIANCES Filed March 21,1962 13 I In Q VA I 7 I l 2 lk\\\\\ 1 13 5 Fig.l

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INVENTOR.

Gino Paren f1.

iawa g ATTQRRIEQS United States Patent DEVICE TO INCREASE THE RESOLVINGPOWER IN PROJECTIONS ON A TRANSLUCENT SCREEN, PARTICULARLY FIT FORPHOTOGRAMMETRIC APPLIANCES Gino Parenti, Rome, Italy, assignor to OtticoMeccanica Italiana Soc. p. Az., Rome, Italy Filed Mar. 21, 1962, Ser.No. 181,247 Claims priority, application Italy, Mar. 22, 1961, 5,018/ 611 Claim. (Cl. 88-2833) There are known in photogrammetric andaerophotogrammetric instrumentations devices for diascopic projection ofimages on plates or films on atranslucent screen, for the purpose ofenlarging them properly and, observing them through transparency, toperform on them images of measurements which in this way may reach ahigh grade precision.

It is therefore necessary to obtain a considerable definition of theprojected images, joined to an almost uniform distribution of theluminous intensity of the screen.

It is known that the definition of the projected images is the greater,the more minute the roughness is of the polish constituting thetranslucent surface on which the image (screen) is formed; on the otherhand, however, the possibility of having the optimum of theabove-mentioned uniformity of luminous intensity is the greater, thegreater within a certain limit, is the roughness ofthis surface(diffusing capacity of the screen).

The purpose of this invention is to ensure a good definition of theprojected images, also to maintain a considerable uniformity of thedistribution of the intensity of the illumination of the screen. Thedescription of the invention may more easily be followed in reference tothe added illustrating design which represents, by way of a not limitedexample, a preferred performance. In the illustration:

FIG. 1 represents a screen mounted on a frame;

FIG. 2 is a section of the same according to the hatched plan IIII ofFIG. 1.

Referring to the figures a screen is represented with such roughness asto ensure a uniform distribution of the luminosity of the image. Saidscreen is mounted on frame 2 on the lower end of which are made twoholes 3, while at the upper end two pivots 4 are fitted free to turn intheir proper seats.

On a supporting plate 5 the motor 6 is fitted of which the turning shaftis made conjoint, by means of a joint 7, with shaft 8 turning in thebearings 9.

In the positions shown in the drawing two endless screws 10 are keyed onshaft 8 in play with as many helicoidal wheels 11. The pivots 4 fittedon frame 2 are clutched in seats 12 eccentrically arranged in thehelicoidal wheels 11.

Two pivots 13 are fixed in the holes 3 and made con- 3,186,299 PatentedJune 1, 1965 joint with plate 5. The arrangement of pivots 13 and thesize of the holes 3, taking into account the eccentricity of pivots 4with respect to the helicoidal wheels 11, are such as to allow the frame2 and therefore the formation plan of the projected image, a uniformcircular movement of which the trajectory, by virtue of the flanges ofpivots 13, constantly will be on the layer located by theabove-mentioned collection plan of the projected image.

A cover 14, whilst it protects the mechanical parts in movement,prevents the observer from seeing this, so that the projected image onscreen 1 appears to him clear and perfectly defined. In fact, owning tothe movement of screen 1, the effect of the roughness of the translucentscreen, will be of less influence to the clearness of the image andtherefore the image will turn out to admit the relief also in thesmallest details. Moreover, the considerable grade of roughness which itwas possible to adopt for the translucent surface of the screen, willpermit to observe the projected image, endowed by luminous intensityalmost uniform from the centre to the margins of the drawing.

The variations of a constructive character which might be applied to thedescribed device will fall into the field of protection of the inventionevery time that the same inventive conception here exposed would becarried out to reach equal or similar results.

What I claim is:

An optical device, comprising a single translucent screen having a roughsurface and adapted to receive a projected image, a frame carrying saidscreen and having two upper corner portions and two lower cornerportions, two symmetrically disposed pivots mounted in said upper cornerportions, a supporting plate, a motor carried by said plate, anelongated shaft driven by said motor, two endless screws keyed upon saidshaft, two helicoidal wheels meshing with said screws, each of saidpivots being eccentrically mounted in a separate helicoidal wheel andbeing rotatable therewith, said two lower corner pontions havingcircular symmetrically disposed uniform holes, and two pivots mounted insaid plate, the two last-mentioned pivots engaging the side walls ofsaid holes and having diameters which are smaller than those of saidholes.

References Cited by the Examiner UNITED STATES PATENTS 1,969,909 8/34Simjian 88-28.9 2,525,596 10/50 Finn 88-28.93 2,780,136 2/57 Erban88-28.93

JULIA E. COINER, Primary Examiner.

NORTON ANSHER, Examiner.

